This invention relates to two-color recording paper, and more particularly to two-color recording paper on which a two-color pattern or picture can be recorded in response to chrominance signals in a facsimile or the like system, and recording method and apparatus utilizing the two-color recording paper.
Conventionally, two-color recording in facsimile apparatuses and printers has been carried out by using, for example, a thermosensitive recording system as disclosed in an article entitled "Thermal recording paper", by Noboru Yamato, THE JOURNAL OF THE INSTITUTE OF IMAGE ELECTRONICS ENGINEERS OF JAPAN, Vol. 4(4), P185 (1975). In such a recording system, two types of leuco dyes having different melting points and hues are added with a developer and various additive materials and coated on a substrate to form thereon two coloring layers, and temperature of a thermal head which consists of arrays of resistive elements is controlled so as to achieve two-color recording in different combinations of hues such as in blue and red and/or black and red.
In the system, however, when red is recorded at a higher temperature, a lower temperature recording color, black for example, appears around each red dot, resulting in a poor color separation and poor picture quality. Moreover, the thermal head which operates at high temperatures wastes in relatively short time. Attempts were made to cope with this problem. For example, discoloring materials which act on the lower temperature developer at temperatures exceeding a predetermined value were used as disclosed in an article entitled "Two-color thermosensitive recording paper", by Kiyoshi Niki et al., The Text for the 3rd National Convention of THE INSTITUTE OF IMAGE ELECTRONICS ENGINEERS OF JAPAN, May 1975. However, this method does not yet attain to solve the above-mentioned problem. The thermal head is heated to much higher temperatures to produce a large temperature difference resulting in a shorter service life. In addition, the scanning speed is slow in this method, since the width of pulses applied is prolonged.
Another two-color recording apparatus used in the facsimile is of an ink-jet recording. This apparatus has already been put in practice; however, it still relies on the mechanical scanning system.